Polyolefin based resin is commonly used for interior furnishings of automobiles such as an installment panel, an airbag cover, a dash board, and the like. To use parts made of polypropylene in automobiles, a coating process is required to match with the color of an automobile. However, since polypropylene is non-polar due to the molecular structure and has high internal crystallinity, it has very low coating adhesion. Therefore, to adhere a desired coating on a substrate made of polypropylene, a chemical or physical treatment process is required.
To improve adhesion of coating on a polyolefin based substrate such polypropylene (PP), polyethylene (PE), and the like, a method of treating hydrofluoric acid and ozone has been used for chemical treatment, and a treatment method such as plasma and corona discharge, and the like has been used for physical treatment. And, flame treatment or primer treatment with a chlorinated polyolefin (hereinafter, referred to as ‘CPO’) resin composition may be conducted before coating. However, the flame treatment is not applied except several countries due to investment cost and space problem because the coating operation should be conducted immediately after the flame treatment and facilities are required. And, the CPO resin raises environmental problem because an organic solvent type coating composition dissolved in an aromatic organic solvent such as toluene, xylene, and the like is used. Thus, an aqueous CPO resin without an organic solvent was developed several years ago, and an aqueous primer using the aqueous COP resin has been gradually applied, and thus a more environment friendly coating composition has been developed. However, these compositions also include halogen, and are deleterious to human body, and thus, there use is limited in several European countries.
Moreover, primer coating treatment is required for adhesion, and the coating is composed of multilayers including additional coatings for physical and chemical properties, and thus, operation time may be increased, cost may be increased due to increase in consumption of a coating composition, thereby increasing cost of the final product.
The present invention provides a solution to the above problems by decreasing cost and providing a material that is more environment-friendly. Most of the currently used compositions are organic solvent based, and thus are harmful to the workers and users, and particularly, to the environment due to their exposure to the air. Further, the CPO resins used to be coated on the polyolefin based material have potential problems due to the chloride being used, which is harmful to the human body. In terms of cost reducing, the conventional composition requires a first coating to enhance adhesion to the polyolefin based material, and a second coating to enhance the physical/chemical properties, while the composition according to the present invention needs only one coating to accomplish the properties.